Shockproof terminal seal



May 23, 1950 R. A. sYKEs SHOCKPROOF TERMINAL SEAL Filed June 18, 1946 A T TORNE V Patented May 23, 1950 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application June 18, 1946, Serial No. 677,451

1 Claim. (01. 1'74 -152) This invention relates 'to contact terminal proxies and more particularly to terminals associatedwith vitreous seals in electrical apparatus.

I n'the electrical arts, the employment of herifieticallysealed units, such as condensers, trans- Iiie'rs, quartz and other crystals, filters and milar apparatus, entails the provision of a pluiality of conductors or terminals sealed through glass to provide a vacuum-tight joint at the terixii'nal "end of the unit. The sealed unit prevents the'eritranee of moisture into the'casing or main- 'ta1'ns"the space in the unit at a controlled pressure and permits the unit to be utilized in cliiiiafteswhere deterioration would otherwise de- 'str'dy the internal elements of the unit or materially affect the operating efiiciency thereof. when the unit is subjected to percussion ef- "fects, such as may be experienced in mobile eliu'ipn'len't, and is designed for removable attachment in holding fixtures, such as sockets,

the shocks to which the unit may be subjected "ma be so severe as to fracture the 'glass seals at the junction of the glass and terminal in the -iihit. The same effects may occur in electronic discharge devices employed in'such'equipment.

object of this invention is to minimize strainsin'the glass seals of such'unitsand devices. Another object of the invention is to prevent shock being communicated to the fragile seals.

A"further object is to prevent fracture of the seals at the juncture of the terminals entering "the'iinit or device.

Another object of the invention is to dissipate ija'ercussion efiects exerted upon the units and devices so that'negligible strain is placed on the seals.

"These objects are attainedin accordance with names of this invention by'providing cushion terminals on the unit or device in combination withihe sealed joint so that the glass is protected lifrom the initial shock'imparted to the terminals.

'8-pparatus mounted within the unit and the outer Tends terminate just beyond the exterior of the glass seals. The exposed stub is joined to 'a closely wound wire helix which is formed to continiie th'e extension of the conductor and provide a "heiiible portion which yields with applied 'i'm being transmitted to the seal.

--2 pact and absorbs 'shock imparted to the terminals of 'the "unit.

A feature of "the invention relates to the combined construction of the terminal assembly whereby the conductor extending through the -seal 'is rigid to insure a strain-free joint in the glass mass 'coaxially'filling the space between the eyelet and the conductor, and the exposed end "of the conductor iscushi'oned-by a resilient sleeve terminal portion which directly engages the socket contacts to mount "the unit in operational equipment. The hollow spiral wire terminal is open atone end to embrace the stub conductor extending through the seal and is rigidly-affixed thereto and the other-end is tapered to form -a closed'contactpoint which'provides'a bearing surface against the interconnecting spring "contact of thesooket assembly. Theclosely wound sleeve insures a substantially rigid thrust terminal along the "axis of the seal under normal conditions so that it performs the same function as if the terminal were solid. However, when excessive shock is imparted to the terminal end of the device the flexible "wire helix is temporarily deformed for "the duration of the "percussion impast so that the shock is dissipated in the spring material of the terminal and is prevented "from The "eyelet terminal construction also "i'na'ybe employed in the metal casing type of electronic discharge device "in which the conductors "for the electrode assembly extend "through the casing.

In one "embodiment of theinventi'on, the rigid "portion of the terminals may be sealed directly in a glass stem of an electronic discharge device and the externalres'ilient sleeveterminal portions connected to "the rigid "portions, to relieve strains and stresses in the glass stem at the sealing Tpoints,'ocoa's1oned by shock 'o'r'impact'incident to testing or operational use of'the device.

7 The various objects, features and advantages of the invention will be more clearly apparent from'the following detailed description when considered in connection with the accompanying drawing. in which:

Fig. 1 shows in elevation a cross-section view of a crystal casing embodying features of this inven- 'tion;

Fig.2 is an enlarged view, partly in'section, oi a termihal'co'nstruction illustrative of this inventionwith a part of the exteriorterminal portion broken away'to'show details of assembly; v

Fig. 3 illustrates, in a perspective view, the stemportion of an electronic discharge device'embodyiiig f eatur'e'sof this invention Fig. 4 shows in a perspective view a portion of the terminal end of a metallic discharge device constructed in accordance with this invention; and

Fig. 5 is a perspective view of an apparatus casing employing a hermetically sealed terminal construction in accordance with this invention.

Referring to the drawings and particularly to Figs. 1 and 2, the terminal assembly of this invention is embodied in a quartz crystal casing l0, for example formed of a metal shell to constitute a protective enclosure for a unit mounted within the casing. The casing is closed at the open end by a terminal base H, for example also of metal, and having a peripheral flange portion reentrant with respect to the casing so that the hat portion oi the base H is flush with the end of the casing ill. The base ll is secured to the casing It by an internal soldered joint H! which seals the conjoint surfaces of the casing and base drawing operation, to form socket openings which are reentrant with respect to the casing.

The sleeves l3 and the annular recess seats l4 formed on the base I I receive metallic eyelets 15, shown more clearly in Fig. 2, which fit into the sleeve portion IS, the eyelet having a flange portion it: which registers with the annular seat is in the base. The eyelet is secured in the sleeve portion inany suitable manner, for example by soldering. A pair of cylindrical metallic conductors I? extend axially through the metallic eyelets l5 and are supported therein by a vitreous annular bead it which is fused in the space between the eyelet and conductor to form an her metic seal along the length of the conductor extending through the eyelet.

The sealed insulating joint is produced preferably by forming the eyelet I5 and conductor ll of a low expansion metal alloy such as nickel, cobalt and iron of an alloy composition commonly known as Kovar and employing a vitreous material, such as borosilicate glass, as the fusible material of the seal, since the metal and glass have substantially the same coefficient of expansion whereby a tight union is effected between the glass and metal elements involved in the seal after the glass bead is sealed or fused thereto. Accordingly, no temperature strains occur in the seal and a hermetically tight joint is realized at the sealing point of the conductor ll. stub conductor I! extending through the seal in the base or terminal end of the casing is provided with a slightly larger diameter head l9 closely adjacent to the termination of the glass seal l8 in the eyelet to form a terminal anchor portion for the conductor. The inner ends of the conductors l1 within the casing are connected to a quartz crystal unit 2i] by support wires 2|, preferably by welding the support wires to the conductors IT. The casing is usually filled with dry air to maintain the electrical characteristics of the crystal constant and after the desired filling is obtained in the device the outlet hole in the top of the casing is sealed by a solder pellet 22.

Since the hermetically sealed crystalrnay be mounted,in one application, in a socket so that it can be readily removable for replacement or substitution, it is usual to provide push type terminal prongs or contacts as continuations of the The rigid Y 4 conductors in the seals for engagement with spring contacts of the socket member. If the crystal assembly is employed in mobile equipment or in other environments where the crystal unit is subjected to percussive impact due to shock or vibrations, it will readily be realized that the mechanical strains imposed on the vitreous seals may cause fracture of the glass mass l8 or setup stresses which result in fracture with consequent deterioration of the hermetic joint and resultant impairment of the atmosphere within the casing. Similarly, in order to determine the adaptability of the crystal unit for usage in specific operational equipment, it is necessary to subject the unit to preliminary mechanical tests before shipment to the customer to determine if the construction can meet the requirement of the test. One example of such a test is the drop" test to observe the effects imposed on the glass seals and thereby avoid hazardous results to the seals during the operating life or" the device.

The fragile glass seals are protected, in accordance with this invention, by providing flexible hollow extensions on the conductors extending through the seals exterior to the device, the

. the head IQ of the rigid conductor IT. The other end is tapered to a point 25 which may be filled with a solder pellet '25 to form a contact surface. The closely adjacent turns of the open end of the extension contact embrace the head IQ of the conductor and are rigidly secured thereto, by

soldering or welding, to provide a firm contact with the conductor I1. The closely wound wire helix beyond the head I9 of the rigid conductor is normally inflexible in an axial direction for small thrust impacts as would be occasioned upon mounting the crystal unit in the socket. On abnormal impact imposed on the helical'extension 23, however, the helix is distorted and the strain set up is absorbed in the spring material of the flexible terminal so that the impact forces are not transmitted to the fragile glass seal and strains or stresses are prevented from producing fracture in the glass mass at the sealed joint to the conductor. This arrangement protects the fragile glass seal from rupture which would cause leakage in the casing and consequent impairment of the crystal unit. The composite conductor terminal for the seals of this invention provides a rigid portion in the vicinity of the seal, which insures a permanent hermetic joint entering the casing, and a flexible shock absorbing terminal portion 23 which is exposed to all the impact hazards incident to operation of the unit in mobile equipment, the flexible hollow terminal dissipating the effects of shock impactso that they never reach the fragile glass seal in the unit casing and, therefore, preserve the pressure condition within the casing. I

The invention is also applicable to electronic discharge devices as shown in Figs. 3 and 4. Fig. 3 shows the base portion of an electron discharge device having an enclosing vessel 21 terminated with a cup-shaped vitreous stem or base 28 with a flat disc portion 29. A plurality of conductors. 11 are sealed to the portion 28 in a circular boundary about a central tubulation 30 which is sealed off after the device is completely evacuated. The conductors I! are connected within the vessel 21 to a plurality of electrodes in an electrode unit, not shown, to supply potentials to the individual electrodes. The fragile seals in the base 29 may be protected, in accordance with this invention, by terminating the short stub conductors I! with flexible terminal contacts 23 to absorb impact shock incident to the conductors and thereby prevent transmission of the shock to the fragile seals of the conductors.

In Fig. 4, the composite terminal assembly, as shown in Fig. 2, may be adapted to an electronic discharge device having a metallic casing 3| in which the base 32 is provided with apertures to receive the eyelets l5 of the sealed terminals.

In Fig. 5, the rectangular casing 33 may be the enclosure for a hermetically sealed unit therein, such as condensers, filters, transformers, switches, relays or other electrical devices which may be deteriorated by moisture or fungus in high, temperature climates or subjected to various changes in temperature and pressure such as is present at high altitude. The hermetic seals in these devices are protected from injury by the composite terminal assembly as herein described.

While the invention has been set forth with respect to a particular embodiment of a push type terminal arrangement adaptable for socket connection, it is, of course, understood that various 6 modifications can be made in the construction to adapt the invention to other methods of connection Without departing from the scope of the invention as defined in the appended claim.

What is claimed is:

A shock-resistant terminal assembly, comprising a rigid conductor hermetically sealed through a glass mass forming a sealed joint, and a wire wound hollow prong having a tapered point, the turns of wire being in contact throughout the length thereof, the open end of said prong being rigidly secured to said conductor adjacent said sealed joint.

ROGER A. SYKES.

REFERENCES CITED The following references are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 1,579,156 Siemann Mar. 30, 1926 2,174,374 Beggs Sept. 26, 1939 2,307,561 Bailey Jan. 5, 19143 2,310,237 Horn Feb. 9, 1943 2,318,435 Stupakoff May 4, 1943 OTHER REFERENCES Wireless World and Radio Review, vol. 17, Sept. 2, 1925, page 283. 

